The International Radio Telegraphic Convention in 1906 adopted the Morse code equivalent of the letters S, O and S as an international maritime distress call. The sequence was chosen because it was distinctive. The letters did not represent any words. Years later, in popular usage, mnemonic phrases were (and still are) often used, such as “Save Our Ship” or “Save Our Souls.” Today, the letters SOS are used widely as a sign for emergency services. Such labels are on emergency telephones or call boxes throughout cities in many countries.